1. Field of the Invention
The present invention relates in general to the telecommunications field and, in particular, to a signaling transfer point (STP) and a method that allows a carrier to reassign trunks (voice circuits) from one switch to another switch without having to inform any other carrier.
2. Description of Related Art
Today many carriers in the telecommunication field need to replace their old switches with new and improved switches that can better handle the ever increasing traffic loads. And, when a carrier replaces an old switch with a new switch they need to move one end of many the trunks (voice circuits) from the old switch to the new switch. In the past, this caused a problem since the carrier needed to inform a remote carrier that supervises a foreign switch at which the other ends of the trunks are connected about the change so they could update a database in the foreign switch. This resulted in an expense to the carrier that moved the trunks because the remote carrier would charge them for their costs in having to update the database in the foreign switch.
To help address this problem, DSC Communications Corporation now part of Alcatel designed a STP known as MegaHub® STP. The MegaHub® STP has a “point code mapping feature” that allows a carrier to reassign one or more trunks from one switch (old switch) to another switch (new switch) in a manner that another carrier would not need to be informed about the change and thus the other carrier would not need to make any changes in the database at the foreign switch. How the MegaHub® STP does this is described below with respect to the block diagram and flowchart shown in FIGS. 1A and 1B.
As shown in FIGS. 1A and 1B (PRIOR ART), the traditional STP 100 receives (step 102a) a call processing message 110 (e.g., Initial Address Message (IAM) 110) on a Signaling System No. 7 (SS7) link 112 from the foreign switch 108. The foreign switch 108 configured the call processing message 110 so it is supposed to be sent by the traditional STP 100 to the old switch 104. However, the traditional STP 100 does not send the call processing message 110 to the old switch 104. Instead, the traditional STP 100 remaps (step 104b) the call processing message 110 such that the remapped call processing message 114 can be sent over a SS7 link 116 to the new switch 106.
To accomplish this, the traditional STP 100 has a processor 118 and a mapping database 120 that implement software to change a value of a Destination Point Code (DPC) in the call processing message 110 to indicate the new switch 106 (shown as new switch “A”) instead of the old switch 104 (shown as old switch “B”). An exemplary message sequence table illustrating how the call processing message 110 can be remapped by the traditional STP 100 is provided below:
DPCOPCCICBX100 → call processing message 110AX100 → remapped call processing message 114where:
DPC is the Destination Point Code.
OPC is the Originating Point Code.
CIC is the Circuit Identification Code.
B is the old switch 104.
A is the new switch 106.
X is the foreign switch 108.
The traditional STP 100 then forwards (step 106b) the remapped call processing message 114 to the new switch 106. Upon receiving the remapped call processing message 114, the new switch 106 seizes (step 108b) the reassigned trunk 102′ (shown as “CIC 100”) associated with the CIC in the remapped call processing message 114. The new switch 106 then sends (step 110b) another call processing message 122 (Address Complete Message (ACM) 122) to the traditional STP 100. The traditional STP 100 remaps (step 112b) this call processing message 122 such that the remapped call processing message 124 looks like it originated from the old switch 104 instead of the new switch 106.
To accomplish this, the traditional STP 100 and in particular the processor 118 and a mapping database 120 implement software to change a value of the Origination Point Code (OPC) in the call processing message 122 to indicate the old switch 104 (shown as old switch “B”) instead of the new switch 106 (shown as new switch “A”). An exemplary message sequence table illustrating how the call processing message 122 can be remapped by the traditional STP 100 is provided below:
DPCOPCCICXA100 → call processing message 122XB100 → remapped call processing message 124
The traditional STP 100 then forwards (step 114b) the remapped call processing message 124 to the foreign switch 108. As can be seen, the foreign switch 108 thinks the trunk 102 is connected to the old switch 104 even though it has been reassigned and is now connected to the new switch 106. After all of this, the foreign switch 108 can established a call using what they believe is the old switch 104 but is in fact the new switch 106. Although the traditional STP 100 works well, it can still be improved so as to give the carrier more flexibility when they reassign and move trunks 102 from the old switch 104 to the new switch 106. An improved STP and method are the subject of the present invention.